The invention relates to a wheel suspension for the driven rear wheels of a motor vehicle comprising a wheel-supporting wheel carrier, which is connected to a vehicle body or an auxiliary frame, and fastened by way of wheel guide members, which are spaced vertically apart from each other; the wheel guide members being arranged above and below a horizontal plane, running through a spin axis, and being employed in such a manner and mounted on the wheel carrier and on the vehicle body that an elastokinematic axis and a kinematic trailing axis are formed at the wheel; the wheel guide members arranged above the spin axis comprise two upper wishbones, which diverge in a direction of body-sided bearings and are disposed in two planes, which are spaced apart, and are hinged to the wheel carrier on both sides of a vertical wheel center transverse plane, and wheel guide members arranged below the spin axis comprise an A-frame arm and a steering tie rod, whereby the A-frame arm is hinged in front of the vertical wheel center transverse plane.
The German Patent Document DE 19 38 850 C3 discloses a wheel suspension, where the upper suspension link plane comprises two open wishbones, diverging in the direction of the longitudinal center axis of the vehicle. The bottom suspension link plane comprises an A-frame arm, whereby the links or the position of the links result in an elastokinematic axis. Furthermore, the US Report on the Sixth International Technical Conference on Experimental Safety Vehicles on Oct. 12, 1976, pages 656 to 664, discloses a wheel suspension with upper open wishbones and a bottom A-frame arm with a steering tie rod, both of which together form an elastokinematic axis and a trailing axis. Furthermore, the German Patent Document DE 37 14 034 C1 discloses a wheel suspension for the driven rear wheels of motor vehicles with upper open suspension links and a bottom A-frame arm with a pendulum support. The result is a pitching pole for starting and braking torque compensation via the body-sided bearings and the wheel carrier-sided bearings of the A-frame arm.
The WIPO Publication WO-A-92/16386 discloses a wheel suspension for the driven, hinged and unhinged rear wheels of a motor vehicle with a wheel carrier, which is supported on the body side by way of a spring strut. Said wheel carrier is guided by way of two single links, forming an upper hinge and a bottom hinge, comprising an A-frame arm, and a steering tie rod link, which runs approximately in the transverse direction of the vehicle. These individual links diverge in the transverse direction of the vehicle and are mounted in two separated joints of the wheel carrier, whereby the A-frame arm is held on the wheel carrier by way of one joint, and the two hinges form an elastokinematic wheel swivel axis and a kinematic swivel axis. The two hinges are arranged and supported in the joints in such a manner that the result is a wheel suspension that guarantees, on one hand, safe vehicle handling under all driving conditions with good driving comfort and, on the other hand, the wheel suspension is supposed to be designed in a spatially compact form in the vehicle.
The problem on which the invention is based is to improve the prior art wheel suspension in such a manner that it can be designed small and compact and can be preassembled and adjusted and guarantees stable vehicle handling both when cornering and driving straight ahead.
The invention solves this problem in that the A-frame arm is located in an inclined plane, formed in the direction of travel; and the steering tie rod is mounted on the wheel carrier behind the wheel center transverse plane; wherein for all forces acting on the wheel, coordinated bearing characteristics of the wheel guide members and the position of the elastokinematic axis in interaction with the trailing axis result in an ideal swivel axis for the wheel; and wherein predetermined directions of movement of wheel carrier-sided bearings of two links of the wheel guide members, result in pole rays, which intersect in front of and above a horizontal plane, running through the spin axis, and form a pitching pole for antidive and antisquat. Other advantageous features are discussed further, below.
The object of the invention is to provide a wheel suspension for the rear wheels of a motor vehicle, in particular for an all terrain vehicle, which guarantees stable driving behavior when cornering and driving straight ahead under forces acting on the wheel. In addition, the wheel suspension is supposed to be designed small and compact and ought to permit preassembly and adjustment.
The major advantages targeted with the invention lie in the fact that the design of the wheel suspension with the upper open links and a bottom A-frame arm with a steering tie rod and with correspondingly coordinated characteristics in the link bearings results in a wheel suspension that guarantees maximum starting and braking torque compensation. Furthermore, when forces act on the wheel, it is possible to make elastokinematic wheel position changes and exert an understeering effect in the toe-in direction for all forces, like lateral forces, braking forces, and Ferraria forces.
To this end, the wheel suspension comprises, in essence, wheel guide members, which are disposed above a spin axis and comprise two open wishbones, which diverge in the direction of the body-sided bearing and are disposed in two planes that are spaced apart. On both sides of a vertical transverse plane of the wheel center the wishbones are hinged to the wheel carrier. Below the spin axis there are other wheel guide members, comprising an A-frame arm and a steering tie rod. When seen in the direction of travel, the A-frame arm is hinged in front of the vertical wheel center transverse plane and is located in an inclined plane in the direction of travel. The steering tie rod is mounted on the wheel carrier behind the wheel center transverse plane. The pole rays, which run perpendicular to the direction of movement of the wheel carrier-sided bearings of the upper and bottom link, result in a pitching pole, which is located in front of and above the plane, running through the spin axis, and results in an antidive and antisquat effect.
The two upper wishbones are designed, for example, as so-called rod links and form with the bottom wheel guide members an elastokinematic axis, where the two upper wishbones form an ideal upper pole for this axis, and the bottom pole, formed by the steering tie rod and the A-frame arm, is located behind the vertical wheel center transverse plane and outside the track width. Owing to these two poles, the elastokinematic axis experiences an intersection point in the wheel contact plane outside the track width and, when seen in the direction of travel, behind the vertical wheel center transverse plane.
The position of the elastokinematic axis is determined in that the one bearing point of the upper link in front of the vertical wheel center transverse plane lies closer to the vertical wheel center transverse plane than the bearing point of the other bearing of the upper wishbone, which lies behind the vertical wheel center transverse plane.
Furthermore, the two upper wishbones form an ideal upper pole; and the wheel carrier-sided bearing of the bottom A-frame arm forms a constructive pole for the kinematic trailing axis. The intersection point of this trailing axis in the wheel contact plane is located in front of the vertical wheel center transverse plane and inside the track width. To this end, the constructive pole, formed by the A-frame arm in the bearing of the wheel carrier, lies, when seen in the direction of travel, in front of the vertical wheel center transverse plane and inside the track width. In contrast, the upper ideal pole is located approximately in the vertical wheel center in the transverse plane and outside the track width. Thus, this trailing axis exhibits an intersection point in the wheel contact plane.
To achieve the specific position of the kinematic trailing axis and the elastokinematic axis, the bearing points of the upper wishbones are arranged on the wheel carrier between the bearing points of the steering tie rod and the A-frame arm. In this respect the wishbones extend so as to diverge in the direction of the body-sided bearings and, in so doing, cross a link arm of the A-frame arm and the steering tie rod.
Thus, the tendency is to achieve an elastokinematic wheel position change for all forces acting on the wheel, because the characteristics of the link bearings, which are coordinated correspondingly, and the position of the elastokinematic axis and the position of the kinematic trailing axis have an impact on the type and amount of this change in the wheel position.
As a function of the geometric configuration of the wheel guide members and the ideal and constructive poles and axes, which are formed thus, the coordinated characteristics of the bearings of the wheel guide members determine the changes in the wheel position under the influences of the forces on the wheel. The result of the position of the elastokinematic axis and the trailing axis for forces acting on the wheel is an ideal axis between these two other axes, namely the elastokinematic axis and the trailing axis, around which the wheel can move elastokinematically under all forces acting on said wheel.
Thus, the body-sided bearings of the A-frame arm exhibit a significantly stiffer characteristic in the radial load direction than the characteristics in the axial load direction. The radial bearing characteristics of both upper wishbones are altogether identical and exhibit a smaller radial characteristic than the bearing characteristics of the body-sided bearings of the A-frame arm. The radial bearing characteristics of the steering tie rod are designed in total stiffer than the radial bearing characteristics of the bottom wishbones.
In the case of lateral and braking forces as well as longitudinal forces, acting in the opposite direction of travel, the coordination of the bearing characteristics and the position of the elastokinematic axis and the trailing axis are supposed to facilitate superimposing a toe-in movement of the wheel on the effect of a toe-out movement of the wheel, in that the wheel can be adjusted in the direction of toe-in. This adjustment takes place then by way of the ideal swivel axis, which is formed by the two axes and which forms spatially between the elastokinematic axis and the trailing axis and exhibits a point of intersection in an area of the wheel contact plane behind the vertical wheel center transverse plane and outside the track width. For negative longitudinal forces (starting forces), which act in the direction of travel, the wheel position is changed in the direction of toe-out.
The formation of a pitching polexe2x80x94relative to the direction of travelxe2x80x94in front of and above the spin axis to achieve an antidive effect, that is to prevent the vehicle from rising during a braking operation, and an antisquat effect, that is to prevent the vehicle from dipping at startup, is achieved through the inclined alignment of the A-frame arm and the position of the two upper wishbones.
The shock absorber or spring strut extends at an oblique angle relative to the vehicle in the direction of the vehicle longitudinal center axis and is arranged between the A-frame arm and the steering tie rod and the two wishbones and rests against the wheel carrier and the vehicle body. The result of this inclined configuration of the spring strut is predominantly a relatively large trunk space and low liftover height of the vehicle.
One embodiment of the invention is depicted in the drawings and is described in detail in the following.